In a tire for trucks or busses with an aspect ratio of 60% or smaller, a large load is applied to the belt layer of the tire due to internal pressure. Accordingly, a fastening effect with which the tire radial growth is suppressed decreases, and thus, deformation increases. As a result, separation tends to occur easily. For this reason, there is need to improve anti-belt-edge-separation performance and suppress tire radial growth of the tires for trucks or busses.
A conventional pneumatic tire that satisfies the above need is disclosed in Patent Document 1. The conventional pneumatic tire P includes a radial carcass reinforcement, on which a crown reinforcing member is placed. The crown reinforcing member includes at least two working crown plies. Plies of each of the working plies are crossed from one ply to the next and form an angle ((α or β) to the circumferential direction. The working crown plies have the widths L32 and L34 each being at least equal to 8.0% of the maximum axial-direction width S0 of the carcass reinforcement. Firstly, an axial-direction continuous ply is arranged between the working ply and the carcass reinforcement closest to the axis of rotation. The axial-direction continuous ply is formed of inextensible metal cables forming an angle of at least δ of 60° to the circumferential direction, and has the axial-direction width L31 at least equal to the axial-direction widths L32 and L34 of the shortest working crown plies. Secondly, a first additional ply is arranged between the two working crown plies. The first additional ply is formed of metallic elements oriented substantially parallel to the circumferential direction, and has an axial-direction width L33 at least equal to 0.7S0 and a tensile elastic modulus at most equal to that of the most extensible working ply. In the conventional pneumatic tire P, a second additional ply is arranged on each of the two edges of the tire P on a radial-direction outer side with respect to the outermost working crown ply so as to cover the a corresponding one of the edges of the first additional ply arranged between the two working plies. Each of the second additional plies is formed of metallic elements oriented substantially parallel to the circumferential direction, and has a small axial-direction width L36.
Patent Document: Japanese Patent Application Laid-open No. 2001-512390